ground source heat pumps

[jellybean]

We have a 3400 sq ft farmhouse on oil fired heating. 27 radiators but we only use about 4 or 5. One big wood burner in upstairs lounge. Use about 2000 litres of oil per year. I am thinking of putting in a ground source heat pump hopefully to give us a more continuous background heat throughout the house and heat the water etc.
We are also in a good windy spot so was wondering if a smallish wind turbine could be used to generate electricity to run the heat pump but in conjunction with some form of battery pack to store the electricity. Have batteries moved on enough these days to be able to fulfil this function sensibly? We also have a 4kw roof mounted solar system.

I know this will be expensive but if the quality is good maybe it would be a viable long term investment. Any comments or ideas from those who have done such a thing would be much appreciated.

 

[Grassman]

I have just built a new bungalow with underfloor heating. 450 metres of pipe heats the house well. Only in very cold weather have we put the log burner on.
However I got caught out with the rhi and am having trouble getting the grant which has spoilt the job somewhat!

PS. That is 160 m2 floor.

 

[jellybean]

This is a barn conversion done in 1989 so definitely not suitable for underfloor heating. I would prefer it to stack up without any RHI if possible. (not that I don't trust the gov. or anything)

 

[slackjawedyokel]

Im sure that someone more knowledgeable will be along shortly, but my understanding of GSHPs (from when we looked into them several years ago) is that they work best (are most efficient) when you're only trying to heat water a little bit so they're better for underfloor heating than radiators. I think if you have them cranked up to output at the temperature you want in your radiators, the electric you end up using to run the thing might make it cheaper to use a standard boiler.
Then again, they may have become much better in the past few years...

 

[Courier]

Can anyone explain how GSHP is worth the extra cost over ASHP . Just curious.

 

[Grassman]

Air source is getting more rhi than it was. Seems to be the system of choice now. Ground source is expensive to install but gives a good steady heat.
How air souce performs when it's -5 outside is beyond me. But I know people with it and they seem happy.

 

[jellybean]

Ground source seemed the obvious choice to me as we have the land, we have a digger and all close to the point of entry in the house where the unit would sit. As @Grassman says how do extract heat from air below freezing temp?
I would not be against installing some more solar panels and a battery bank if it was efficient and cost effective. Presumably a super insulated water tank provides a thermal store and the batteries an electricity store. Just a question of sorting the wheat from the chaff with advisers and suppliers and seeing if it is do-able.
With regard to the ground source being best suited to underfloor heating we do not require the house to be hot, merely comfortable, particularly as we get older. Typical indoor temp in winter would be 15-17 degrees. My bedroom is whatever the temp is outside; window always open, radiator has never been turned on.

 

[akaPABLO01]

Both are good and will perform if correctly sized including heat emitters (rads)

Ashp will be capped at 20,000kWh and gshp at 25,000kWh but gshp may be able to circumvent regulations if used as district heating. A better understanding will be known closer to 20th September.

Firstly you'll need a heat loss calculation done including rad spec. Once you have this you'll know the system size needed.

With regards to heat pumps cost to run, efficiency, and temperature output depends on flow temp. Flow temp of 45 does gives a cheaper cost, most systems run at 50 though and water at 60. All temps can be adjusted. Summer, a lower flow temp, winter higher.

You could even look at hybrid, keep your water on your current system and heat from ashp.

Currently market conditions are seeing a large amount of ashp being installed with gshp second. The difference is outlay cost. Gshp cost considerably more but appeal in district heating application qualifying for 20 years tariff whereas ashp only qualify for 20 years if 200kW is built. A large system otherwise only 7 year tariff.

Savings are made on gshp when you do the groundwork as all my farmers usually do.

It doesn't cost anything to get a few quotations together

http://www.microgenerationcertification.org/consumers/installer-search

 

[Exfarmer]

My air source heat pump is great in Summer
useless in winter! a frozen block of ice most of the day

 

[akaPABLO01]

My air source heat pump is great in Summer
useless in winter! a frozen block of ice most of the day

Do you adjust flow temperature?

 

[Exfarmer]

Do you adjust flow temperature?

I have played a little , but nothing dramatic, do you think this could cure it?

 

[akaPABLO01]

i would run the flow at 45 in spring summer and early autumn and look to increase it by 5 degrees experimenting. Make sure your condense pipework is well insulated usually the white pipe leading to the drain at the base of the unit.

Remember the higher the flow the less scop your unit will do. This means it will cost more to run the unit. Also check the system defrost mode using the data sheet .pdf you'll be able to find online by the manufacturer.

 

[Exfarmer]

i would run the flow at 45 in spring summer and early autumn and look to increase it by 5 degrees experimenting. Make sure your condense pipework is well insulated usually the white pipe leading to the drain at the base of the unit.

Remember the higher the flow the less scop your unit will do. This means it will cost more to run the unit. Also check the system defrost mode using the data sheet .pdf you'll be able to find online by the manufacturer.

Thanks I will try it.

 

[phillipe]

Unless you have a well insulated house ,you are wasting your money

 

[foxbox]

Unless you have a well insulated house ,you are wasting your money

Not this nonsense again?

Without RHI GSHP is difficult to justify but with RHI it's much easier. Our GSHP heats 4 properties and runs at around 50C (provides heating and hot water to each); it qualifies for RHI and is on track to provide a very attractive ROI over the RHI period. All of our properties are heated with wall mounted radiators (some were replaced but most are the originals) and so far the system has been virtually faultless. There is a page on our blog; there is also a nice explanation of how heat pumps work on there too. Our log cabin is heated with an air source heat pump; it's kept the cabin warm at -12C but I'd make a pretty big assumption that it wasn't running very efficiently when it did that!

 

[phillipe]

Not this nonsense again?

Without RHI GSHP is difficult to justify but with RHI it's much easier. Our GSHP heats 4 properties and runs at around 50C (provides heating and hot water to each); it qualifies for RHI and is on track to provide a very attractive ROI over the RHI period. All of our properties are heated with wall mounted radiators (some were replaced but most are the originals) and so far the system has been virtually faultless. There is a page on our blog; there is also a nice explanation of how heat pumps work on there too. Our log cabin is heated with an air source heat pump; it's kept the cabin warm at -12C but I'd make a pretty big assumption that it wasn't running very efficiently when it did that!

May i ask what sort of electric bill do you get of do you have solar aswell?

 

[suffolksmallholder]

55 degrees is the magic heat figure, this is cheap heat. After this temp it all costs more. Good insulation helps so does draught proofing. I'd only ever fit a GSHP to a complete refurb or new build.
SS

 

[Mur Huwcun]

We've just put groundsource loops in this summer, photos on the TAW thread. It will be heating a 30sq m new build extension and a similar size old stone build existing house. We have fitted serious floor insulation and underfloor heating throughout. The new build has 75mm celotex in the cavity, 100mm insulation under floor slab and 50mm between floor slab and underfloor screed. Lofts have 400mm min insulation (200mm rolls running criss cross). All windows are A++++ whatever spec etc.

We are yet to switch it on and commission the system but I'm looking forward to see how it goes. We will be fitting a log burner aswell in the lounge and this room has been zoned separately on the UF in order to maximise the use of the woodburner if need be. Heatpump has not arrived yet so can't comment on that but all pipework and buffer tanks are in. 400m of groundloops and a 8kw output HP.

 

[jellybean]

Interesting replies, thank you. We have someone coming out today to look at the situation and see what's possible.

 

[f0ster]

you need to compare the cop(coefficient of performance) of these, they give a cop at different outside temperatures such as -2 for example with a water demand of 50 deg for example. by comparing this data you can see whose gives the best performance at low temps, most of them give a cop of about 4to1 when the weather is good but it is when the outside temperature gets down to zero that sorts out the better machines, some machines can get down to less than 2 to 1 cop, also quite a few of them have an electric immersion heater in them to give you the last 10 deg of hot water,